1. Field
The present disclosure relates generally to laser systems and, in particular, to a method and apparatus for laser systems using disks to reflect light. Still, more particularly, the present disclosure relates to a method and apparatus for laser systems using disks to reflect light with cryogenic cooling.
2. Background
A laser system produces a high-intensity optical, infrared, or ultraviolet radiation with photons as a result of stimulated emission maintained within a solid, liquid, or gaseous medium. The emitted light is coherent. The emitted light can be manipulated with lenses. “Coherent light” is light having in-step waves of identical frequency and phase. The beam of coherent light generated by a laser system differentiates the laser system from other light sources that emit incoherent light beams. The other light sources emit light beams that have random phase varying with time and position.
A laser system includes a gain medium that is located inside a reflective optical cavity, as well as a means to supply energy to the gain medium. The gain medium is a material with properties that allow it to amplify light by stimulated emission. A cavity has two mirrors arranged such that light bounces back and forth, each time passing through the gain medium. The cavity may have additional mirrors. Typically, one of the two mirrors is partially transparent or is physically divided into two or more optics, one of which is reflective, and one transmissive. This type of mirror is also referred to as an “output coupler”. The output laser beam is emitted through this mirror.
Light of a specific wavelength that passes through the gain medium is amplified. Amplified is an increase in power. The mirrors ensure that most of the light makes many passes through the gain medium. Part of the light that is between the mirrors passes through the partially transparent mirror and escapes as a beam of light.
A laser system uses optics to reflect light through the lasing medium. The optics include at least a pair of mirrors located at the ends of the lasing medium. The first of these mirrors will reflect laser light to the second mirror, while the second end mirror splits the laser light approaching on it into two portions: A laser beam which is taken out of the laser system, and a reflected beam that is redirected back into the laser medium and then to the first mirror. The reflected beam is continuously amplified and this amplified beam is returned to the second mirror for continuing the generation of the laser beam.
Different types of laser systems are present. These laser systems include, for example, gas lasers, chemical lasers, dye lasers, metal-vapor lasers, solid-state lasers, and semiconductor lasers. A solid-state laser system uses a gain medium that is a solid, rather than a liquid, such as in dye laser systems or a gas as in gas laser systems. A disk laser is a type of solid-state laser system that has a heat sink and laser output that are realized on opposite sides of a layer of gain medium. Power scaling for disk laser systems may be limited by amplified spontaneous emissions (ASE). Amplified spontaneous emissions occurs when the lasing medium emits light spontaneously, and this light is amplified by the gain medium independent of the lasing process. Amplified spontaneous emissions are the light that enters the gain medium, is transmitted through the gain medium, and reflected with a different direction as the path defined by the lasing device. The path defined by the lasing device is the desired path of the laser. Power scaling is the act of increasing the power.
Accordingly, it would be advantageous to have a method and apparatus which takes into account one or more of the issues discussed above, as well as possibly other issues.